Centrifugal separation of heavy boiler oil



2 SHEETS-SHEET 1- I/IAVII 2 '11 III/j G. H. ANDERSSON CENTRIFUGAL SEPARATION OF HEAVY BOILER OIL Oct. 23, 1951 Filed Aug. 19, 1948 lnven/or Gus/av Harry Andersson W24 Alb/megs G. H. ANDERSSON 2,572,425

CENTRIFUGAL SEPARATION OF HEAVY BOILER OIL Oct. 23, 1951 2 SHEETS-I-SHEET 2 Filed Aug. 19, 1948 [raven/or Gusfav Harry Andersson B9 ,9 w m, fiuvr Af/crneys Patented Oct. 23, 1951 cENrniFUoAL SEPARATION OF BOTILERI OIL HEAVY Gustav Har y 'Andersson, Smedslattemfiweden,

Sweden, .a corporation of Sweden assignor to Aktiebolaget Separator, Stockholm,

Application August 19, 1948, Serial No. 5,085

InGreatBritain August-28, 1947 ,2 Claims.- -1 This invention relates tea method and apparatus for so purifying heavy boiler oil that it can, be used as a fuel'iorndiesel engines" or for as turbines.

Heavy boiler oil iseonsiderahly -cheaper than the so-called diesel .oil normally used-in diesel engines, and for a longtimepast, attempts have been made to use boiler oil-inplace of diesel oil. However, owing to the failureytofree the boiler oil sufiiciently from the solid impurities andwater which it contains, it use in diesel engines has :caused heavy wear ofpiston rings and cylinder liners, leading to excessive'repair costs.

1 ;By the practice of. the: present invention,1it is possible tofree the boilerbil-from solid impurities :and water to-a degree sufficient to make it possible to use heavy boiler'oil for diesel engines withoutcausing excessive wear. According to the invention, theoil is heated to a temperature hi h enough to break any emulsion existing innit,

whereupon the oil is purified bycentrituging in two stages. In the first stage, watenanda con.- siderabie art of the solid impurities are removed ina centrifugal bowl provided with arrangements for continuous discharge ofwater :as

the heavier component. However, "since "the specific-gravity of the heavy boilenoi-il of thelsind in question is-very this-hand "almostias highas that of water, the equilibrium between ,oil; and water in the bowl is unstable so that, for the slightest reason, the border layer betweenthese liquids is displaced radially within widerlimits. Such displacement may be caused, for'example, if during the separating operation there is a change in the proportion between the amount of oil and water. Small variations in the throughput rate may alsoentail the same result, and even a change of the separating temperature may cause a displacement.

The displacement of the border layer between 1 the liquids may be reducedby so dimensioning the separate oil and water discharge channels in the bowl that the aflord a minimum resistan e to .the flow of the respective liquids, and byproviding members, for example, in the form 'of wings, which prevent the liquidsjfromwslipping. Even when these measures are'takem. excessive radial displacement of the boundary layer may sometimes occur. In case the boundary layer is positioned relatively near to the centerl'of ,the bowl or the axis of rotation, this may result'in reduction of the strength of the power field for the separation of solid particles from the oil, and also in reduction of the space within which this power field is effective. Although the oil is sufficiently freed from water when the boundary layer is positioned relatively near to the bowl center, the oil will notthen be .sufilciently freedvfrom solid particles.

According tothe invention, the oilfreed'from waterlis therefore treated in a second centrifugingstage in a clarifier. type bowl. The characteristic feature of such .a bowl is that the oil forced to pass through a set of .discsalong their entire radial extent, that is from the-outer edge of the discs totheir inner edge. With this secondary treatment of the .oil, the heavier solid impurities, for example, ash substances, are with certainty separated completely enough'to ensure that the purified oil, when used for. fueling diesel engines, does not cause excessivewear.

In the practice of one form of the invention, the purification of 'bOilGI'aOiliS considerably improved by carrying out the second separation at a substantially lower temperature than the first separation. After the first separation has been effected, thexoil is chilled, or-allowed to cool off, so that the asphalt substances dissolved inrthe oil are precipitated. In the second'separation,

:the decrease of temperature between the separations-should be at leastr10 F. The first separation may be carried out ,at about F., althoughzthis temperature will vary according to the viscosity and other, qualities ofthe oil.

In the accompanying drawings, Fig. 1 is a schematic view, partly in vertical section, of an apparatus for carrying out the newvprocess; and Fig. 2 is an enlarged vertical sectional view ofthe first-stage centrifugal bowl shown in Fig. l.

Referring to the drawings, the first :stage centrifuge has a centrifugal bowl In which receives the boiler oil from -a stationary'feed pipe H connected to the bowl inlet througha flexible air-tight seal I 2. From the bowl inlet, the oil passes down through a central distributor l3 having radial wings l3a,'and through openings [3b in the distributor to the separating chamber or locus of centrifugal force Illa, which contains a set of conical discs M having distributing holes Ma overlying the holes I312. The water and solid impurities separated from the oil between the conical discs 2 I The oil from the discharge passages l6 iscon e 4 merely illustrated the sealing arrangements schematically in Fig. 1.

I claim:

1. A method of purifying boiler oil to a degree suflicient for its use in diesel engines and gas turbines, which comprises heating the oil to a temperature at which any emulsions thereof are broken, then feeding the oil to a first-stage locus of centrifugal force and there separating from it water and a substantial part of the solid impurities, continuously and separately discharging from the locus said water with its contained imducted through pipe l8 to thebowl 19 of the second stage centrifuge. The pipe [8 is connected to the oil discharge passage [6 through an air-tight connection which may be of any conventional form. As shown schematically, itincludes part of the flexible seal I2 and a lower flexible seal 18a. Intermediate its ends the pipe l8 extends through a cooler 18b, to reduce the temperature of the oil as previously. described. At its discharge end, the pipe l8'is connected to the inlet ,of bowl I9 through a flexible seal l2a. The bowl I 9, which is of the clarifier type, has a central into the separating chamber or locus of centrifugal force I9a at a region outside a set of Thus, the oil must flow inwardly throughthe. disc spaces and along the entire radial extent of the discs in order to reach the oil discharge passage 22. During this inward flow, solid'impurities remaining after the first separation are separated from the oil between the discs 2| and collect in the outer part'of the bowl. The purified oil is conducted away by a stationary pipe 23 having an air-tight connection with the discharge passage 22, such connection, as illustrated schematically, including part of the flexible seal 12a and a lower flexible seal 23a.

By thus dimensioning the oil and water discharge passages in the first-stage bowl l0, and

.by providing these passages with the radial wings ISa-and [6a, the position of the boundary surface between the oil and water in the bowl It! may be maintained substantially constant. Even when this improved separator is used, however, the feed of liquid to the separator should be kept as constant as possible, and it is therefore advisable to pump the oil into the separator by means of a pump having a fixed volumetric capacity, corresponding to the capacity of the separator. For example, a gear wheel pump may be used, the speed of which is so adjusted as to'obtain the desired throughput.

The method and apparatus of the invention may be used to purify boiler oil not only for use as diesel engine fuel but also for use in fueling gas turbines. A it is very important that fuel oil for gas turbinesis not in any way aerated, the centrifuges to be used for the treatment of such oil should be provided with inlet and outlet pipes for the oil which are hermetically connected to the bowl, so that the oil is not exposed tothe infiuence of the air. Also, so-called paring discs can be used for this purpose. Since centrifuges of the type in which the bowl inlet and outlet connections are sealed against admission of air to the product are well known in the art, I have puri ies, as a heavier component, and the oil as a lighter component, feeding the discharged oil to a second-stage locus of centrifugal force and there passing it'inwardly through a setof superimposed disc spaces and along the entire radial extent of said spaces from their outer to their inner edges, collecting and retaining in the outer part of the second-stage locus the remaining ing the oil to an asphalt-precipitating temperature during its passage from the first-stage to the second-stage locus, whereby precipitated asphalt substances resulting from said cooling are sepafrated from the oil in said disc spaces and carry with them at least some of said remaining solid impurities. V I

2. A method of purifying boiler oil to a degree sufficient for its use in diesel engines and gas turbines, which comprises heating the'oil to a temperature at which any emulsions thereof are broken, then feeding the oil to a first-stage" locus of centrifugal force and there separating from it water and a substantial part of the solid impurities, continuously and separately discharging from the locus said'water with its contained impurities," as a heavier component, and the'oil as a lighter component, feeding the discharged oil to a second-stage locus of centrifugal force and there passing it inwardly through' a set of superimposed disc spaces and along theentire radial extent of said spaces from their outerto their inner edges, collecting and retaining in the outer part of the second-stage locus there maining solid impuritiesseparated from the oil dur ing its inward flow through the spaces, discharging the purified oil from the second-stage locus, and maintaining the oil out of contact with air during its flow to and from said centrifugal loci and during the separations therein.

GUSTAV HARRY ANDERSSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Hanno Apr. 19, 1949 

